CD40L expression is skewed on polarized Th1/Th2 cells. Purified CD4⁺ T cells were stimulated on day 0 with bead-adsorbed anti-CD3 and anti-CD28 mAb under Th1- or Th2-polarizing conditions. (A) On day 12, CD40L expression was measured and cells were restimulated as on day 0 (n = 16). CD40L expression was measured again on day 13 (n = 16) and day 16 (Th1 n = 5; Th2 n = 16). The mean ± SE is shown. (B) CD40L expression was measured at 0 hours (day 12) and following restimulation under the same nonpolarizing conditions used for PBMC cultures. Data are expressed relative to the 6-hours Th1 sample. Due to overlap of the data points, not all symbols are visible. Solid bars indicate the mean (n = 4). Standard error bars are shown.